Liquid crystal display and method for manufacturing the same

ABSTRACT

The liquid crystal display apparatus according to the present invention includes a) the direction of the twist angle of molecule orientation of the twisted phase difference board ( 3 ) is reverse to the direction of the twisted orientation of the liquid crystal molecule of the liquid crystal devices ( 2 ), and the twist angle of the twisted phase difference board is smaller than the twist angle of the liquid crystal devices ( 2 ) by 10° to 40°; b) an angle between the liquid crystal molecule-oriented direction of the alignment film ( 23   a ) of the second substrate and the molecule-oriented direction of a lower polymer ( 32   b ) of the liquid crystal polymer layer lies in the range of 80° to 90°; c) an angle between an absorption axis of the first polarization board ( 1 ) and the liquid crystal molecule-oriented direction of the alignment film ( 23   b ) of the first substrate side lies in the range of 50° to 60°; d) an angle between the absorption axis of the second polarization board ( 4 ) and the molecule-oriented direction of an upper polymer ( 32   a ) of the liquid crystal polymer lies in the range of 30° to 40°; and e) the relationship between Δnd 1  of the nematic liquid crystal layer and Δnd 2  of the liquid crystal polymer layer is defined in a particular relationship, so that it is possible to resolve colored image on the display and to realize an image quality having a high contrast.

TECHNICAL FIELD

The present invention relates to a liquid crystal display apparatus anda method for manufacturing the same. In particular, it relates to aliquid crystal display apparatus and a method for manufacturing the samewhich defines an optimum arrangement of STN-type liquid crystal devicesand structural components each connected to the liquid crystal devices,in order to realize a high quality image. The present invention can beadvantageously applied to a liquid crystal display unit used in aportable terminal, a game apparatus used as a toy, etc.

BACKGROUND ART

For example, an STN-type liquid crystal apparatus has been disclosed inJapanese Unexamined Patent Publication No. 7-191296 (published date:Jul. 28, 1995, “A liquid crystal apparatus”). This liquid apparatusincludes a display cell holding a nematic liquid crystal layer between afirst substrate having a first transparent electrode and a secondsubstrate having a second transparent electrode, and an opticalanisotropic member for correcting a phase difference structured using apolymer film or a compensating liquid crystal cell between a secondpolarization board and the second substrate which are provided between afirst polarization board and the second polarization board.

According to this document, the nematic liquid crystal layer of thedisplay cell (corresponding to the liquid crystal devices) is twistedand oriented by 120° or more, and a twist angle and a retardation Δnd ofthe optical anisotropic body are set to predetermined conditions inaccordance with the twist angle of the nematic liquid crystal layer andthe retardation Δnd which is obtained by a product of a doublerefractive index Δn and a gap “d” between substrates, so thatundesirable color on the display, occurring during a turned on/off stateof the liquid crystal devices, can be resolved.

In this document, however, since the twist angle and the retardation Δndof the optical anisotropic member (corresponding to the twisted phasedifference board) are set in accordance with the twist angle and theretardation Δnd of the nematic liquid crystal layer, the following items(1) to (6) have not yet defined concretely. That is, (1) a relationshipof an angle between a direction of the twist angle of the twisted phasedifference board and the direction of the twist angle of the liquidcrystal device; (2) the relationship of the angle between an orienteddirection of the liquid crystal molecule of an alignment film of thesecond substrate and a molecule-oriented direction of a lower polymer ofthe twisted phase difference board; (3) the relationship of the anglebetween an absorption axis of the first polarization board and theoriented direction of the liquid crystal molecule of the alignment filmof the first substrate; (4) the relationship of an angle between anabsorption axis of the second polarization board and the orienteddirection of the molecule of an upper polymer of the twisted phasedifference board; (5) the relationship between the double refractiveindex of the nematic liquid crystal layer and the double refractiveindex of the twisted phase difference board; and (6) preferential viewangles at the liquid crystal layer of the liquid crystal device.Accordingly, in this document, an optimum display quality has not yetbeen realized for resolving undesirable color on the display occurringduring the turned on/off state of the liquid crystal device.

DISCLOSURE OF THE INVENTION

The purpose of the present invention is to provide a liquid crystaldisplay apparatus which can resolve undesirable color on the display andcan realize bright and high contrast image quality, based on dataobtained through various experiments, by defining concretely therelationship of each angle described in the above items (1) to (6).

Another purpose of the present invention is to provide a method formanufacturing the above liquid crystal display apparatus which caneffectively determine a cutting size of a material (below,material-cutting) for the structural component based on the structure ofthe above liquid crystal display apparatus so that it is possible toconsiderably reduce the manufacturing cost and to improve theproductivity when manufacturing the liquid crystal display apparatus.

According to the first aspect of the present invention, in the liquidcrystal display apparatus comprising a first substrate having a firsttransparent electrode and a second substrate having a second transparentelectrode; liquid crystal devices holding the nematic liquid crystallayer which is twisted and oriented by the twist angle of the STN(preferably, in the range of 180° to 270°) between the first and secondsubstrates; the first polarization board which is provided for anoutside of the first substrate; the twisted phase difference boardhaving the liquid crystal polymer layer and provided for the outside ofthe second substrate; and the second polarization board provided for theoutside of the twisted phase difference board.

The twisted direction of the twist angle of the molecule orientation ofthe twisted phase difference board is reverse to the direction of thetwisted orientation of the liquid crystal molecule of the liquid crystaldevices, and the twist angle of the twisted phase difference board isstructured with an angle smaller than the twist angle of the liquidcrystal device by 10° to 40°.

Preferably, an angle between the oriented direction of the liquidcrystal molecule of the alignment film of the second substrate and themolecule-oriented direction of the lower polymer of the liquid crystalpolymer layer lies in the range of 80° to 90°, and the angle between theabsorption axis of the first polarization board and themolecule-oriented direction of the alignment film of the first substratelies in the range of 50° to 60°, and further the angle between theabsorption axis of the second polarization board and themolecule-oriented direction of the upper polymer of the liquid crystalpolymer layer lies in the range of 30° to 40°.

Further, preferably, in the relationship between the retardation Δnd1which is obtained by the product of the double refractive index Δn1 ofthe nematic liquid crystal layer and the thickness d1 of the liquidcrystal layer, and the retardation Δnd2 which is obtained by the productof the double refractive index Δn2 of the liquid crystal polymer layerand the thickness d2 of the liquid crystal polymer layer, theretardation Δnd1 lies in the range of 0.7 to 0.9 μm, and the differenceΔnd1−Δnd2 lies in the range of 0.1 to 0.3 μm.

Still further, preferably, the direction of the preferential view angleof the liquid crystal device is set to any one direction, with referenceto a clock face, at two-thirty, four-thirty, seven-thirty, or ten-thirtyo'clock.

Still further, preferably, the second polarization board and the twistedphase difference board structures a bonding unit. In the bonding unit,by utilizing the fact that the angle between the absorption axis of thesecond polarization board and the molecule-oriented direction of theupper polymer of the liquid crystal polymer layer lies in the range of30° to 40°, the second polarization board structured of a rolled filmand the twisted phase difference board also structured of a rolled film,are superposed on each other and bonded in the same roll-out direction.After bonding to each other, the bonding unit can be obtained by cuttingto a predetermined size.

Still further, preferably, the liquid crystal polymer layer of thetwisted phase difference board has a temperature compensatingcharacteristic in which the retardation Δnd2 is always smaller than theretardation Δnd1 of the nematic liquid crystal layer in a predeterminedtemperature range (preferably, 20° C. to 80° C.).

According to the second aspect of the present invention, in the methodfor manufacturing the liquid crystal display apparatus comprising thefirst substrate having the first transparent electrode and the secondsubstrate having the second transparent electrode; the liquid crystaldevices holding the nematic liquid crystal layer which is twisted andoriented by the twist angle of the STN (preferably, in the range of 180°to 270°) between the first and second substrates; the first polarizationboard which is provided for an outside of the first substrate; thetwisted phase difference board having the liquid crystal polymer layerand provided for the outside of the second substrate; and the secondpolarization board provided for the outside of the twisted phasedifference board; wherein the angle between the absorption axis of thesecond polarization board and the molecule-oriented direction of theupper polymer of the liquid crystal polymer layer lies in the range of30° to 40°,

-   -   a) structuring the second polarization board in the shape of a        rolled film;    -   b) structuring the twisted phase difference board in the shape        of a rolled film;    -   c) by utilizing the fact that the angle lies in the range of 30°        to 40°, arranging the roll-out direction of the rolled film of        the second polarization board so as to become the same roll-out        direction of the rolled film of the twisted phase difference        board;    -   d) superposing the rolled film of the second polarization board        on the rolled film of the twisted phase difference board, and        adhering these rolled films when simultaneously rolling out        these rolled films; and    -   e) manufacturing the bonding unit structured by the second        polarization board and the twisted phase difference board by        cutting the bonding unit to the predetermined size after an        adhesion step.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is an essential structural view of the liquid crystal displayapparatus of the present invention;

FIG. 2 shows data of various angles when performing experiments 1 to 7by changing angles arranged between the twisted phase difference boardand the polarization board using the twisted phase difference board usedin the present invention;

FIG. 3 shows data of the relationship of the arranged angles when adesirable display image was finally obtained based on the data shown inthe following FIGS. 4 to 10, and is shown by the data expressed based inthe same manner as shown in FIG. 2;

FIG. 4 is a graph which corresponds to experiment 1 in FIG. 2 forindicating the relationship between the retardation Δnd and thetransmission factor of the twisted phase difference board;

FIG. 5 is a graph which corresponds to experiment 2 in FIG. 2 forindicating the relationship between the retardation Δnd and thetransmission factor of the twisted phase difference board;

FIG. 6 is a graph which corresponds to experiment 3 in FIG. 2 forindicating the spectral transmission factor and the relationship of thearranged angle of the upper polarization board;

FIG. 7 is a graph which corresponds to experiment 4 in FIG. 2 forindicating the supply voltage/transmission factor and the relationshipof the arranged angle of the upper polarization board;

FIG. 8 is a graph which corresponds to experiment 5 in FIG. 2 forindicating the supply voltage/transmission factor and the relationshipof the arranged angle of the lower polarization board;

FIG. 9 is a graph which corresponds to experiment 6 in FIG. 2 forindicating the spectral transmission factor showing the result of theabove-mentioned data;

FIG. 10 is a graph which corresponds to experiment 7 in FIG. 2 forindicating the spectral transmission factor based on the relationshipbetween the twisted phase difference board and the twist angle;

FIG. 11 is a graph of the spectral transmission factor of the liquidcrystal display apparatus using a uniaxial-oriented film;

FIG. 12 is an explanatory view for schematically explaining therelationship of the arranged angle which is shown by experiment 1 inFIG. 2;

FIG. 13 is an explanatory view for schematically explaining therelationship of the arranged angle which is shown by experiment 2 inFIG. 2;

FIG. 14 is an explanatory view for schematically explaining therelationship of the arranged angle which is shown by experiment 3 inFIG. 2;

FIG. 15 is an explanatory view for schematically explaining therelationship of the arranged angle which is shown by experiment 4 inFIG. 2;

FIG. 16 is an explanatory view for schematically explaining therelationship of the arranged angle which is shown by experiment 5 inFIG. 2;

FIG. 17 is an explanatory view for schematically explaining therelationship of the arranged angle which is shown by experiment 6 inFIG. 2;

FIG. 18 is an explanatory view for schematically explaining therelationship of the arranged angle which is shown by experiment 7 inFIG. 2;

FIG. 19 is an explanatory view for schematically explaining therelationship of the arranged angle which corresponds to “FINAL 1” inFIG. 3;

FIG. 20 is an explanatory view for schematically explaining therelationship of the arranged angle which corresponds to “FINAL 2” inFIG. 3;

FIG. 21 is an explanatory view for schematically explaining therelationship of the arranged angle which corresponds to “FINAL 3” inFIG. 3;

FIG. 22 is an explanatory view for indicating evaluation of the imagequality of the liquid crystal display apparatus which is provided by therelationship of the arranged angles of “FINAL 1” to “FINAL 3” shown inFIG. 3;

FIG. 23 is a chromaticity diagram indicating a white color at the turnedoff state of the supply voltage for the liquid crystal device;

FIG. 24 is a chromaticity diagram indicating a black color at the turnedon state of the supply voltage for the liquid crystal device;

FIGS. 25A and 25B are views for explaining a problem which occurs whencutting the upper polarization board and the twisted phase differenceboard in a conventional art, and FIGS. 25C and 25D are views forexplaining cutting these boards according to the present invention;

FIG. 26 is an explanatory view for explaining cutting of the upperpolarization board and the twisted phase difference board in an actualmanufacturing method of the liquid crystal display apparatus accordingto the present invention;

FIG. 27 is an essential structural view in which a reflection board isadded to the liquid crystal display apparatus shown in FIG. 1;

FIG. 28 is an essential structural view in which a touch panel is addedto the liquid crystal display apparatus shown in FIG. 1;

FIG. 29 is a graph for explaining the temperature characteristic of thetemperature compensating type liquid crystal polymer layer and theretardation of the nematic liquid crystal layer; and

FIG. 30 is a graph for explaining the contrast in use of the liquidcrystal polymer layer having the temperature compensation.

BEST MODE FOR CARRYING OUT THE PRESENT INVENTION

The preferred embodiments of the present invention will be explainedwith reference to the drawings below.

FIG. 1 is an essential structural view of the liquid crystal displayapparatus according to the present invention. In the drawing, referencenumber 1 denotes a first polarization board, 2 is a liquid crystaldevice, 3 is a twisted phase difference board, and 4 is a secondpolarization board. The liquid crystal device 2 is structured by holdingthe liquid crystal layer 24, and by the first substrate 21 b and thesecond substrate 21 a, the first transparent electrode 22 b and thesecond transparent electrode 22 a, and the first alignment film (lower)23 b and the second alignment film (upper) 23 a. Further, the twistedphase difference board 3 is structured by coating the liquid crystalpolymer on the transparent film substrate 31 b, performing alignmentprocess at high temperature so as to obtain a desirable twisted angle,rapidly cooling and fixing it, and coating the hardcoart layer 31 a.

In this example, the twisted phase difference board 3 is providedbetween the liquid crystal device 2 and the second polarization board 4,and the following is explained with respect to this arrangement.However, since the same effect can be obtained if the twisted phasedifference board 3 is provided between the liquid crystal device 2 andthe first polarization board 1, the explanation is omitted.

Further, the twisted phase difference board 3 has a characteristic whichcan adjust freely and independently the retardation for the direction ofthe thickness. The present invention defines the above-mentioned optimumrelationship of the angle based on various experiments explained belowby utilizing the above-mentioned characteristics. As the twisted phasedifference board 3, a model “LC film” which was provided by NIPPONPETROLEUM & CHEMICAL CO., LTD. and is available in the market, was used.

FIG. 2 shows data of various angles when performing experiments 1 to 7by changing various conditions, i.e., the relationship of the arrangedangles, using the twisted phase difference board 3 used in the presentinvention. In this experiment, a horizontal axis (an x-axis) at thedirection of the hands showing just three o'clock is defined as 0°, theangle for anticlockwise is defined as “plus”, and the angle forclockwise is defined as “minus”. The following FIGS. 4 to 10 show thedata when changing the retardation and wavelength in accordance with theabove angle conditions.

Further, FIG. 3 shows data of the relationship of the arranged angleswhen a desirable display image was finally obtained based on the datashown in FIGS. 4 to 10. In FIG. 3, the best quality of the display imagecan be obtained in the relationship of the angle shown by “FINAL”, andit is possible to realize low cost apparatus.

In FIGS. 2 and 3, the “upper (second) polarization board” corresponds tothe second polarization board 4 in FIG. 4; the “twisted phase differenceboard” corresponds to the twisted phase difference board 3 in FIG. 3;the “upper polymer molecule” corresponds to the upper polymer 32 a inFIG. 1; the “lower polymer molecule” corresponds to the lower polymer 32b in FIG. 1; the “liquid crystal cell” corresponds to the liquid crystaldevice 2 in FIG. 1; the “upper liquid crystal molecule” corresponds tothe liquid crystal molecule in the second alignment film 23 a in FIG. 1;the “lower liquid crystal molecule” corresponds to the liquid crystalmolecule in the first alignment 23 b in FIG. 1; and the “lower (first)polarization board” corresponds to the absorption axis of the firstpolarization board 1 in FIG. 1.

The data of the experiment numbers 1 to 7 in FIG. 2 are shown in thegraphs shown in FIGS. 4 to 10. That is, the experiment number 1corresponds to FIG. 4; the experiment number 2 corresponds to FIG. 5;the experiment number 3 corresponds to FIG. 6; the experiment number 4corresponds to FIG. 7; the experiment number 5 corresponds to FIG. 8;the experiment number 6 corresponds to FIG. 9; and the experiment number7 corresponds to FIG. 10. Further, FIG. 11 shows data of the phasedifference board used in the prior art, and is provided for comparingthe effect of the present invention with that of the prior art.

In the following explanations, a twist angle 240° is used for all liquidcrystal cells, and the retardation Δnd1 is 0.84 μm. UP is the angle ofthe absorption axis of the upper (second) polarization board, LP is theangle of the absorption axis of the lower (first) polarization board,and LCP is the liquid crystal polymer.

When the STN is used as the liquid crystal device, it is preferable touse the twist angle in the range of 180° to 270°. This is because, whenthe twist angle exceeds 270°, an increase in failures of the alignmentand deterioration of the response characteristic are confirmedexperimentally, and deterioration of the slope of the characteristic arealso confirmed experimentally at the angle 180° or less. Although thetwist angle 240° was used in this embodiment according to the presentinvention, if the twist angle lies in the range of 180° to 270°, it isconfirmed that the present invention can be applied to the liquidcrystal.

In FIG. 4, the ordinate is transmission factor, and the abscissa isretardation Δnd2 of the liquid crystal polymer layer (twisted phasedifference board), and this graph shows the relationship between thetransmission factor and the retardation Δnd in the case of the UP beingin the range of +35° to +75° and the LP being −15° (fixed). In thiscase, for other angles, the upper polymer molecule is −70°, and thelower polymer molecule is +70° as shown by the experiment number 1 inFIG. 2.

As shown in the drawing, when the UP is +75°, and when the retardationΔnd2 is 0.45 μm, the maximum brightness is 0.248.

As mentioned above, when the UP is +75°, and when the retardation Δnd2is 0.45 μm, the maximum brightness 0.248 was obtained. However, thewhite color which is very close to the blue color is found in thespectral characteristic of the above data, and this was undesirablevisually.

In FIG. 5, as well as FIG. 4, the ordinate is transmission factor, andthe abscissa is retardation Δnd2 of the liquid crystal polymer layer,and this graph shows the relationship between the transmission factorand the retardation Δnd in the case of the UP being in the range of +35°to +75° and the LP being −15° (fixed). In this case, for other angles,the upper polymer molecule is −80°, and the lower polymer molecule is+60° as shown by the experiment number 2 in FIG. 2.

As shown in the drawing, when the UP is +45° and +55°, and when Δnd isabout 0.55 μm, the maximum brightness (0.258) is obtained.

As explained above, although the brightness becomes maximum when the UPis +450 (550) and when Δnd is about 0.55 μm, these values areinsufficient visually to obtain the desirable image.

In FIG. 6, an ordinate is transmission factor, and an abscissa iswavelength of the light, and this graph shows the spectralcharacteristic of the white color when the UP is in the range of +35° to+75° and the LP being −15° (fixed), and the retardation Δnd being 0.6μm. In this case, the upper polymer molecule is −80°, and the lowerpolymer molecule is +60°. As shown in the drawing, when the UP is +35°,a high transmission factor is obtained in long wavelength of about 600nm or more. When the UP is +75°, the maximum transmission factor isobtained in the wavelength of about 500 nm. Further, the transmissionfactor is decreased in the wavelength of about 500 nm or more. Asexplained above, the spectral characteristic of the white color (tint)fluctuates widely. However, when the UP is +45° (dotted line), theconstant and high transmission factor can be obtained in the wavelengthof about 500 nm or more. That is, it is possible to obtain the whitecolor having stable characteristic.

In FIG. 7, the ordinate is transmission factor, and the abscissa issupply voltage, and this graph shows the relationship between thetransmission factor and the supply voltage in the case of the UP beingin the range of +35° to +75° and the LP being −15° (fixed), and theretardation Δnd1 of the liquid crystal device is 0.6 μm. In this case,the upper polymer molecule is −80°, and the lower polymer molecule is+60°. As shown in the drawing, when the supply voltage is about 2v(within the range from 2v to a point P), and when the UP is +55°,leakage of the light becomes less when the liquid crystal device isturned on, and the contrast (a ratio of the transmission factors of theblack and white) becomes good. The UP (an upper polarization board) isset to +50° after visually taking account the white color.

In FIG. 8, the ordinate is transmission factor, and the abscissa issupply voltage, and this graph shows the relationship between thetransmission factor and the supply voltage when the UP is +50° (fixed),the LP is in the range of −5° to −25°, and the retardation Δnd1 of theliquid crystal device is 0.6 μm. In this case, the upper polymermolecule is −80°, and the lower polymer molecule is +60°. As shown inthe drawing, when the LP is small, the white color becomes bright, but ablack color is hard to obtain. Accordingly, when the LP is about −10°, agood result can be obtained.

In FIG. 9, the ordinate is transmission factor, and the abscissa is awavelength of light, and this graph shows the relationship between thetransmission factor and the wavelength when the UP is +50° (fixed), theLP is −10° (fixed), and the retardation Δnd1 of the liquid crystaldevice is 0.6 μm. The supply voltage is used as a parameter. In thiscase, the upper polymer molecule is −80°, and the lower polymer moleculeis +60°.

As shown in the drawing, when the supply voltage is changed in the rangeof 0v to 2.2v, the spectral characteristic becomes normal white at 0volt, and is also normal at the halftone in the range of 2.0v to 2.05v.Further, the spectral characteristic becomes black with a slightly bluecolor (this is because the transmission factor does not reach 0v, asshown by arrows).

In FIG. 10, the ordinate is transmission factor, and the abscissa is awavelength of light. This graph shows the relationship between thetransmission factor and the wavelength in the case that the twist angleof the twisted phase difference board is +200° (in the above mentionedcase, this angle is +220°). Further, this graph shows the relationshipwhen the UP is +40° (fixed), the LP is −15° (fixed), and the retardationΔnd1 of the liquid crystal device is 0.6 μm. The supply voltage is usedas a parameter. In this case, the upper polymer molecule is −100°, andthe lower polymer molecule is +60°.

As shown in the drawing, when the supply voltage is changed in the rangeof 0v to 2.2v, the spectral characteristic becomes the normal white at 0volt, and the desirable black can be obtained in the range of 2.1v to2.2v (this is because the transmission factor reaches perfectly 0 whenthe wavelength is about 500 nm.

In FIG. 11, the ordinate is transmission factor, and the abscissa is awavelength of light. This graph shows the relationship between thetransmission factor and the wavelength when the supply voltage is usedas the parameter in the liquid crystal display apparatus using the phasedifference board of a conventional uniaxial oriented film. This is aproduct specification of the phase difference board made of a uniaxialoriented polycarbonate film which is used in the conventional product bythe applicant. In this example, however, since the white color (when thesupply voltage is 0v) becomes light blue, the halftone becomes lightbrown and the black color is changed to blue from brown, it is necessaryto improve the conventional phase difference board (as shown by arrows,the transmission factor does not reach 0, and a color close to blackremains.

FIGS. 12 to 18 are explanatory views for schematically explainingarrangement relationships (angles) shown in FIGS. 4 to 10. That is, FIG.12 corresponds to the experiment 1 of FIG. 2, FIG. 13 corresponds to theexperiment 2 of FIG. 2, FIG. 14 corresponds to the experiment 3 of FIG.2, FIG. 15 corresponds to the experiment 4 of FIG. 2, FIG. 16corresponds to the experiment 5 of FIG. 2, FIG. 17 corresponds to theexperiment 6 of FIG. 2 and FIG. 18 corresponds to the experiment 7 ofFIG. 2.

Further, FIGS. 19 to 21 correspond to FIG. 3. That is, FIG. 19corresponds to “FINAL 1”, FIG. 20 corresponds to “FINAL 2”, and FIG. 21corresponds to “FINAL 3”.

Still further, in FIGS. 12 to 21, the “lower polarization board”corresponds to the first polarization board 1 of FIG. 1, the “liquidcrystal cell” corresponds to the liquid crystal device 2 of FIG. 1 andthe “phase difference board” corresponds to the twisted phase differenceboard 3 of FIG. 1, and the “upper polarization board” corresponds to thesecond polarization board 4 of FIG. 1.

In this example, as shown in the drawing, the twist angle between theupper liquid crystal molecule 23 a and the lower liquid crystal molecule23 b was set to set to 240° as mentioned above. Further, the twist anglebetween the upper polymer molecule 32 a and the lower polymer molecule32 b of the phase difference board was set to either 220° or 200°.

As mentioned above, the “FINAL 3” is the best in viewpoints of displayquality and cost performance.

FIG. 22 is a view for explaining an evaluation of image quality of theliquid crystal display apparatus using the 220°-twisted phase differenceboard and the 200°-twisted phase difference board which were preparedbased on the angle relationship of “FINAL 1” to “FINAL 3” shown in FIG.3. FIG. 23 is a chromaticity diagram which shows the white color whenthe supply voltage to the liquid crystal device is turned off. FIG. 24is a chromaticity diagram which shows the black color when the supplyvoltage to the liquid crystal device is turned on.

In FIG. 22, each of values x and y is the value on the chromaticitydiagram shown in FIGS. 23 and 24. As shown in the drawing, when the220°-twisted phase difference board is used, it is possible to improvenot only white color (value Y), but also the halftone. According to theevaluation based on the viewpoint of an observer, the characteristic ofthe view angle can be improved, and the image quality becomes very good.Further, when the 200°-twisted phase difference board is used, thecontrast can be improved. Accordingly, the twist angle of the phasedifference board is preferable in the range of 200° to 230°. That is,when the twist angle of the phase difference board is set to the anglesmaller than that of the liquid crystal device (for example, 240°) inthe range of 10° to 40°, the contrast can be improved. On the otherhand, when the twist angle of the phase difference board becomessmaller, the contrast becomes worse and it is not preferable.

FIG. 23 is a chromaticity diagram explaining the relationship betweenthe retardation Δnd1 of the liquid crystal layer and the white colorwhen the supply voltage to the liquid crystal layer is turned off. Inthe drawing, 755 and 770 are values of the retardation Δnd1, and areshown by 0.755 μm and 0.770 μm. As shown in the diagram, 755 ispositioned on the dark yellow-green in the diagram. 770 is positioned onthe light yellow-green in the diagram. 800 and 840 are positioned on thegreen-yellow close to the white in the diagram. 900 and 1000 arepositioned on the yellow-white in the diagram.

FIG. 24 is a chromaticity diagram explaining the relationship betweenthe retardation Δnd1 of the liquid crystal layer and the black colorwhen the supply voltage to the liquid crystal layer is turned on. Aswell as the above, in the diagram, 770 and 800 are values of theretardation Δnd1, and are shown by 0.770 μm and 0.800 μm. 770 and 800are positioned on the intermediate of the blue. 900 is positioned ongreen-blue close to white in the diagram. 1000 is positioned onblue-green close to white in the diagram. Accordingly, although theblack having the retardation Δnd1 of 770 to 990 μm is colored slightlyblue, a good black can be obtained on the display. However, when theretardation Δnd1 is larger than 900 nm, the black is close to green andit is not preferable. Further, as explained in FIGS. 4 and 5, thedifference between Δnd1 and Δnd2, i.e., Δnd1−Δnd2, is preferable in therange of 0.1 to 0.3 μm, in particular, 0.2 to 0.3 μm.

Next, a manufacturing method of the liquid crystal display apparatusaccording to the present invention is explained with reference to thedrawings. FIGS. 25A and 25B are views for explaining problems inmaterial-cutting in the conventional art when cutting the upperpolarization board (formed by a rolled film) and the twisted phasedifference board (also structured by a rolled film). FIGS. 25C and 25Dare views for explaining material-cutting according to the presentinvention.

As explained in detail below, in the conventional art, therewasconsiderable loss in material-cutting when superposing the twistedphase difference board on the upper polarization board. That is, sincethere is the relationship between the molecule-oriented direction of theupper polymer and the direction of the absorption axis of the upperpolarization board in the liquid crystal polymer layer of the twistedphase difference board, the above two rolled films cannot be directlysuperposed upon each other as they stand, in the same rolling direction(i.e., roll-out direction) of the twisted phase difference board and theupper polarization board, so that there were considerable loss inmaterial-cutting. Accordingly, this results in increase of parts cost ofthe liquid crystal display apparatus. In the present invention, it ispossible to adhere and wind the twisted phase difference board and theupper polarization board for the same roll-out direction without loss atthe material-cutting of the twisted phase difference board so that it ispossible to reduce the cost of the liquid crystal display apparatus. Thepresent invention is explained in detail below.

FIG. 25A shows arrangement relationship between the upper polarizationboard 4 and the upper polymer 32 a shown in FIG. 18. That is, the arrow“a” is the direction of the absorption axis (i.e., a moving direction ofthe rolled film) of the upper polarization board, and the direction ofthe arrow “a” has +40° for the x-axis. On the other hand, the arrow “b”the direction of the molecule orientation (i.e., the moving direction ofthe rolled film), and the direction of the arrow “b” has −100° for thex-axis.

Accordingly, as mentioned above, since the upper polarization board ofthe rolled film and the twisted phase difference board of the rolledfilm have the angle relationship between the absorption axis and theoriented direction, they cannot be superposed on each other in the samedirection (i.e., roll-out direction). In this case, the upper polymermust be inclined by 140° for the rolled film of the upper polarizationboard in order to superpose on each other as shown by FIG. 25B.Accordingly, when manufacturing an individual display apparatus, thereis considerable loss in the material-cutting when superposing andcutting.

Further, FIG. 25B is a detailed explanatory view of FIG. 25A. Thearrangement relationship between the upper polarization board 4 and theupper polymer 32 a is the same as that of FIG. 25A. As well as FIG. 25A,the arrow “a” is +40° for the x-axis of the twisted phase differenceboard, and the arrow “b” is −100° for the x-axis. In this case, as shownby the angles a1 and a2, the upper polymer must be produced based on theoriented direction of ±40° for the moving direction “b” of the rolledfilm in the manufacture of the twisted phase difference board itself.Accordingly, when the angle relationship between the upper polarizationboard and the upper polymer is 140°, they must be inclined andsuperposed on each other as shown in FIG. 25B so that there isconsiderable loss in material-cutting.

In the present invention, as shown in FIGS. 20 and 21, the angledifference between the absorption axis of the upper polarization boardand the molecule-oriented direction of the upper polymer is set to −40°,and the oriented direction of 40° (i.e., angles a1 and a2) of the rolledfilm of the upper polymer itself is utilized positively so that it ispossible to realize the same moving direction of the rolled film of theupper polarization board as that of the rolled film of the twisted phasedifference board.

That is, FIG. 25C shows an arrangement relationship between the upperpolarization board 4 and the upper polymer 32 a in FIG. 20. That is, thearrow “a”indicates the direction of the absorption of the upperpolarization board, and has −45° for the x-axis. On the other hand, thearrow “b” indicates the molecule-oriented direction of the upperpolymer, and has −85° for the x-axis of the twisted phase differenceboard. Accordingly, the angle difference between them is 40°. Therefore,when the rolled film of the upper polymer having the oriented directionof 40° is used, the rolled film of the upper polarization board and therolled film of the upper polymer can be superposed upon each other forthe same direction.

Further, FIG. 25D shows an arrangement relationship between the upperpolarization board 4 and the upper polymer 32 a shown in FIG. 21. Thatis, the arrow “a” has +90° for the x-axis of the twisted phasedifference board, and the arrow “b” has +50° for the x-axis of thetwisted phase difference board. Accordingly, the angle differencebetween them is 40°. Therefore, when the rolled film of the upperpolymer having the oriented direction of 40° is used, the rolled film ofthe upper polarization board and the rolled film of the upper polymercan be superposed upon each other in the same direction. Further, whencutting the rolled film for each size, since it is cut only at a rightangles to the rolled film, it is possible to utilize almost all rolledfilm without loss in material-cutting, and to realize low cost product.

FIG. 26 is an explanatory view in the case of actual manufacture of therolled films in FIGS. 25C and 25D. As shown in the drawing, the rolledfilms of the upper polarization board and the upper polymer are moved tothe same direction, superposed upon each other and adhered. Then, thesuperposed rolled film is cut off for each size so that the polarizationboard with the phase difference board can be manufactured (see dottedline (1)). As another case, the rolled films are superposed upon eachother and wound, and cut off it to a suitable size in order tomanufacture a bonded unit of the polarization board and the twistedphase difference board. As a result, it is possible to considerablyreduce material-cutting loss, and to improve productivity, so that it ispossible to achieve reduction in the manufacturing cost.

FIG. 27 is an essential and structural view of the liquid crystaldisplay apparatus in which a reflection board is added to the structureof FIG. 1. In general, aluminium is evaporated onto a thin substrate,such as a paper, an aluminium foil, etc., and this aluminium-coatedsubstrate is used as the reflection board 5. As another example of thereflection board, a half-transmission type reflection board, in whichthe aluminium is coated onto a transparent substrate, is used. In thiscase, a back light (not shown) is usually used in addition to thereflection board.

FIG. 28 is an essential and structural view of the liquid crystaldisplay apparatus in which a touch panel is added to the structure ofFIG. 1. The touch panel 6 is usually bonded to the upper polarizationboard 4. In the liquid crystal display apparatus according to thepresent invention, since a high contrast can be realized, it is veryeasy to observe the image without deterioration of the image qualityeven if a touch panel 6 is provided.

FIG. 29 is a graph for explaining a temperature compensating type liquidcrystal polymer used as one modified example and a temperaturecharacteristic of the retardation of the nematic liquid crystal layer.The twisted phase difference board, in which the retardation Δnd2 is notchanged even if the temperature is changed, was used in this embodiment.However, by using the temperature compensating type liquid crystalpolymer in which the retardation Δnd2 becomes small when the temperatureraises, it is possible to provide a liquid crystal display apparatuswhich shows better temperature characteristic. It is obvious that thedifference between the retardation Δnd1 of the nematic liquid crystallayer and the retardation Δnd2 of the temperature compensating typeliquid crystal polymer is constant in the temperature range of 20° C. to80° C.

In order to resolve an undesirable colored image on the displayapparatus and obtain the high contrast, it is desirable to have the samecharacteristic between two retardations Δnd as far as possible.According to the liquid crystal polymer (LCP) used in the presentinvention, two retardations Δnd are matched in this temperature range sothat it is possible to realize the image having high quality. In thepresent invention, the difference between two retardations, i.e.,Δnd1−Δnd2, are defined in the range of 0.1 to 0.3 μm, and this range isdefined when the temperature is 25° C. However, the present inventioncan be applied in the temperature range of 20° C. to 80° C.

FIG. 30 is a graph for explaining the contrast in use of the temperaturecompensating type liquid crystal polymer. When the temperaturecompensating type liquid crystal polymer and the liquid crystal cellused in the modified example of the present invention are combined witheach other, a deterioration of the contrast is not found as shown in thedrawing.

POSSIBILITY OF UTILIZATION IN INDUSTRY

According to the present invention, as mentioned above, based on resultsof various experiments, the colored image on the display can be resolvedby defining concretely various angle relationships, such as relationshipbetween the twist angles, so that it is possible to provide the liquidcrystal display apparatus having bright and high contrast. Further,based on the structure of the liquid crystal display apparatus mentionedabove, it is possible to perform, very effectively, material-cutting ofthe structural parts so that it is possible to provide a manufacturingmethod of the liquid crystal display apparatus in which the reduction ofthe manufacturing cost and the improvement of the productivity can berealized. As a result, the possibility of utilization in industry isvery good in various fields.

In the present invention, the preferential viewing angle of the liquidcrystal device by an observer can be any one of the following positions,based upon the convention of the face of a clock: two-thirty,four-thirty, seven-thirty, or ten-thirty o'clock, as shown in FIG.21(5).

1. A liquid crystal display apparatus comprising a liquid crystal devicewhich includes a first substrate having a first transparent electrode asecond substrate having a second transparent electrode and a nematicliquid crystal layer which is twisted-oriented by an STN-twist anglebetween the first and second substrates; a first polarization boardprovided outside of the first substrate; a twisted phase differenceboard provided outside of the second substrate and having liquid crystalpolymer layers; and a second polarization board provided outside of thetwisted phase difference board; wherein: the direction of the twistangle of molecule orientation of the twisted phase difference board isreverse to the direction of the twisted orientation of the liquidcrystal molecule of the liquid crystal devices, and the absolute valueof the twist angle of the twisted phase difference board is smaller thanthe absolute value of the twist angle of the liquid crystal devices by10° to 40°.
 2. A liquid crystal display apparatus as claimed in claim 1,wherein the STN-twist angle lies in the range of 180° to 270°.
 3. Aliquid crystal display apparatus as claimed in claim 2, wherein an anglebetween the liquid crystal molecule-oriented direction of the alignmentfilm of the second substrate and the molecule-oriented direction of alower polymer of the liquid crystal polymer layer lies in the range of80° to 90°; an angle between an absorption axis of the firstpolarization board and the liquid crystal molecule-oriented direction ofthe alignment film of the first substrate side lies in the range of 50°to 60°; and an angle between the absorption axis of the secondpolarization board and the molecule-oriented direction of an upperpolymer of the liquid crystal polymer lies in the range of 30° to 40°.4. A liquid crystal display apparatus as claimed in claim 2, wherein inthe relationship between a retardation Δnd1 obtained by product of adouble refractive index Δn1 of the nematic liquid crystal layer and athickness d1 of the liquid crystal layer, and a retardation Δnd2obtained by product of the double refractive index Δn2 of the liquidcrystal polymer layer and the thickness d2 of the liquid crystal polymerlayer, the retardation Δnd1 lies in the range of 0.7 to 0.9 μm, and thedifference Δnd1−Δnd2 lies in the range of 0.1 to 0.3 μm.
 5. A liquidcrystal display apparatus as claimed in claim 2, wherein an anglebetween the liquid crystal molecule-oriented direction of the alignmentfilm of the second substrate and the molecule-oriented direction of alower polymer of the liquid crystal polymer layer lies in the range of80° to 90°; an angle between an absorption axis of the firstpolarization board and the liquid crystal molecule-oriented direction ofthe alignment film of the first substrate side lies in the range of 50°to 60°; an angle between the absorption axis of the second polarizationboard and the molecule-oriented direction of an upper polymer of theliquid crystal polymer lies in the range of 30° to 40°; and in therelationship between a retardation Δn1 obtained by product of a doublerefractive index Δn1 of the nematic liquid crystal layer and a thicknessd1 of the liquid crystal layer, and a retardation Δnd2 obtained byproduct of the double refractive index Δn2 of the liquid crystal polymerlayer and the thickness d2 of the liquid crystal polymer layer, theretardation Δnd1 lies in the range of 0.7 to 0.9 μm, and the differenceΔnd1−Δnd2 lies in the range of 0.1 to 0.3 μm.
 6. A liquid crystaldisplay apparatus as claimed in claim 3 or 5 wherein the secondpolarization board and the twisted phase difference board structures abonded unit; and the bonded unit is structured by superposing upon thesecond polarization board of the rolled film and the twisted phasedifference board of the rolled film, and adhering them for the sameroll-out direction, by utilizing the angle between the absorption axisof the second polarization board and the molecule-oriented direction ofthe upper polymer of the liquid crystal polymer layer being in the rangeof 30° to 40°.
 7. A liquid crystal display apparatus as claimed in claim6, wherein the bonded unit is structured by superposing upon the rolledfilms each other and adhering them for the same direction, and bycutting it to a predetermined size.
 8. A liquid crystal displayapparatus as claimed in claim 2, wherein the liquid crystal polymerlayer of the twisted phase difference board has a temperaturecompensating characteristic in a predetermined temperature range.
 9. Aliquid crystal display apparatus as claimed in claim 8, wherein theliquid crystal polymer layer has a temperature compensatingcharacteristic in which the retardation (Δnd2) of the liquid crystalpolymer layer is always smaller than the retardation (Δnd1) of thenematic liquid crystal layer in a predetermined temperature range.
 10. Aliquid crystal display apparatus as claimed in claim 9, wherein thepredetermined temperature range lies in the range of 20° to 80°.
 11. Aliquid crystal display apparatus as claimed in claim 2, wherein aviewing angle of the liquid crystal apparatus by an observer can be atany one of the following positions, based upon the convention of aclock-face: one-thirty, four-thirty, seven-thirty, or ten-thirtyo'clock.
 12. A liquid crystal display apparatus comprising a firstsubstrate having a first transparent electrode and a second substratehaving a second transparent electrode, a liquid crystal device holding anematic liquid crystal layer which is twist-oriented by an STN-twistangle in the range of 180° to 270° between the first and secondsubstrates; a first polarization board provided outside of the firstsubstrate; a twisted phase difference board provided outside of thesecond substrate and having liquid crystal polymer layers; and a secondpolarization board provided outside of the twisted phase differenceboard; a) the direction of the twist angle of molecule orientation ofthe twisted phase difference board is reverse to the direction of thetwisted orientation of the liquid crystal molecule of the liquid crystaldevice, and the absolute value of twist angle of the twisted phasedifference board smaller than the absolute twist angle of the liquidcrystal devices by a range 10° to 40°; b) an angle between the liquidcrystal molecule-oriented direction of the alignment film of the secondsubstrate and the molecule-oriented direction of a lower polymer of theliquid crystal polymer layer lies in the range of 80° to 90°; c) anangle between an absorption axis of the first polarization board and theliquid crystal molecule-oriented direction of the alignment film of thefirst substrate side lies in the range of 50° to 60°; d) an anglebetween the absorption axis of the second polarization board and themolecule-oriented direction of an upper polymer of the liquid crystalpolymer lies in the range of 30° to 40°; e) in the relationship betweena retardation Δnd1 obtained by product of a double refractive index Δn1of the nematic liquid crystal layer and a thickness d1 of the liquidcrystal layer, and a retardation Δnd2 obtained by product of the doublerefractive index Δn2 of the liquid crystal polymer layer and thethickness d2 of the liquid crystal polymer layer, Δnd1 lies in the rangeof 0.7 to 0.9 μm, and the difference Δnd1−Δnd2 lies in the range of 0.1to 0.3 μm; f) the second polarization board and the twisted phasedifference board structure a bonded unit; and the bonded unit isstructured by superposing upon the second polarization board of therolled film and the twisted phase difference board of the rolled film,adhering them for the same roll-out direction, and cutting it to apredetermined size; and g) the liquid crystal polymer layer has atemperature compensating characteristic in which the retardation (Δnd2)of the liquid crystal polymer layer is always smaller than theretardation (Δnd1) of the nematic liquid crystal layer in apredetermined temperature range.
 13. A method for manufacturing a liquidcrystal display apparatus comprising a first substrate having a firsttransparent electrode and a second substrate having a second transparentelectrode, a liquid crystal device holding a nematic liquid crystallayer which is twist-oriented by an STN-twist angle in the range of 180°to 270° between the first and second substrates; a first polarizationboard provided outside of the first substrate; a twisted phasedifference board provided outside of the second substrate and havingliquid crystal polymer layers; and a second polarization board providedfor the outside of the twisted phase difference board; wherein an anglebetween an absorption axis of the second polarization board and amolecule-oriented direction of an upper polymer of the liquid crystalpolymer layer lies in the range of 30° to 40°; wherein: a) the secondpolarization board is structured by rolled film; b) the twisted phasedifference board is structured by rolled film; c) the roll-out directionof the rolled film of the second polarization board and the roll-outdirection of the rolled film of the twisted phase difference board arearranged in the same direction by utilizing an angle in the range of 30°to 40°; d) the rolled film of the second polarization board and therolled film of the twisted phase difference board are superposed uponeach other and adhered in the roll-out direction; and e) a bonding unitis made by cutting the rolled film in a predetermined size afteradhesion and bonding the second polarization board and the twisted phasedifference board.